# Copyright 2020 The PyTorch Lightning team and The HuggingFace Team. All rights reserved.

# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
import re

from pytorch_lightning.utilities import _module_available

nltk = None
if _module_available("nltk"):
    import nltk

    nltk.download("punkt", quiet=True)


def add_newline_to_end_of_each_sentence(x: str) -> str:
    """This was added to get rougeLsum scores matching published rougeL scores for BART and PEGASUS."""
    re.sub("<n>", "", x)  # remove pegasus newline char
    assert nltk, "nltk must be installed to separate newlines between sentences. (pip install nltk)"
    return "\n".join(nltk.sent_tokenize(x))
